WASHINGTON -- A drug withdrawn from clinical trials because of safety concerns was helping regrow nerve fibers in the brain of a man with Parkinson's disease, scientists report.

The finding probably will renew debate over the drug, GDNF. It had offered encouragement to people with Parkinson's who reported improvement when using it in trials. But the drug was withdrawn by the manufacturer, Amgen, this year.

Seth Love, Steven S. Gill and colleagues at Frenchay Hospital in Bristol, England, report in Monday's issue of the journal Nature Medicine that an autopsy of the brain of one of the patients who received the drug in an early trial shows that nerve fibers that are lost in the disease were growing back.